Ceramic filter candles are tubular filter elements closed at one end and are well known for use in removing particulates from hot gasses in which such particulates are entrained. Such filter elements as known in the prior art have included a porous ceramic tubular support structure having a less porous skin provided on the outer surface thereof for capturing particulates on the outer portion of the skin as a particulate laden gas passes from the outside to the inside of the element through the skin and the underlying support structure. During such use particulates collect on the outer surface of the element and form a porous cake which adheres to the exterior of the filter element. When the thickness of the cake becomes so great as to affect adversely the efficient operation of the associated filter, the cake must be removed in a cake removal operation. In one such cake removal operation known as a back wash, the flow of gas through the wall of the filter element is reversed so that the gas passes from the inside of the element to the outside and physically blows the cake from the external portion of the filter element where it has collected.
Inasmuch as ceramic filter elements are at times weak in tensile strength, the pressure differential applied across the wall of the filter element during the backwash cleaning operation must be maintained below that value which would result in the eruption or cracking of the filter element, and that pressure is oftentimes less than that which would otherwise be used for the quickest and most efficient cleaning of the filter element. Also, ceramic filter elements of the tubular or candle type known in the prior art are relatively fragile and must, therefore, be handled very carefully during shipment and storage and during installation in a filter tank or the like.
It would be desirable, therefore, to provide a gas filter element which is able to withstand the high temperatures generally encountered in high temperature gas filtration, which is generally stronger and less susceptible to breakage during normal handling, and which is appreciably stronger in tensile strength than are the filter elements known in the prior art so as to enable the use of higher pressure differentials during a high pressure back wash operation.